The parity of the pion from .

We can determine the internal parity of the pion by studying **pion capture by a deuteron**,
The pion is known to have spin 0, the deuteron spin 1, and the neutron spin
.
The internal parity of the deuteron is +1.
The pion is captured by the deuteron from a 1S states, implying
in the initial state.
So the total angular momentum quantum number of the initial state is
.

So the parity of the initial state is

The parity of the final state is

Therefore,

Because the neutrons are identical fermions, the allowed states of two neutrons are , , , The only state with is the state, so

Jim Branson 2013-04-22